This invention relates generally to control systems, and more particularly to a controller for controlling flow, speed, pressure or performance of a pumping system.
A typical centrifugal pump of the prior art comprises an impeller, rotatably mounted in a stationary casing with the rotating impeller imparting pressure and kinetic energy to the fluid being pumped, and the stationary casing guiding the fluid to and from the impeller. In a typical centrifugal pump casing, which generally includes concentric, diffusor and volute type centrifugal casings, the rotation of the impeller imparts kinetic energy to the fluid and causes fluid flow, in a generally circular direction about the perimeter of the impeller, through the casing surrounding the impeller. At some point in the casing, the fluid flows from the perimeter of the impeller, passes a cut-water or the like through an area of the pump generally known as the discharge inlet area and through the discharge nozzle to the pump discharge.
The fluid flow can be affected by the design of the impeller, the design and size of the casing, the speed at which the impeller rotates, and design and size of the pump inlet and outlet, quality and finish of the components, presence of a casing volute and the like. In order to control fluid flow, variable frequency devices have been used to adjust the motor speed of the pump so as to regulate the flow within the pump system. It is to be noted that, as used herein, variable frequency drives are to include adjustable frequency drives (AFDs), Variable Speed Controllers (VSCs) or something similar, which operate to control electronic motor speed.
Pump speed and pressure represent important pumping system parameters, in addition to flow, which can cause the pump to operate at less than its most efficient level. Even more disadvantageously, less than optimal operating parameters may cause the pump and motor to work harder and thus wear out quicker, thereby shortening the pump""s operational lifetime. According, it is highly desirable to provide a computer-controlled variable frequency device (VFD) controller which utilizes computer algorithms and sensor inputs to control flow, speed, pressure and performance of a pumping system by monitoring motor, pump and system parameters and controlling pump output via speed variations. It is also advantageous to obtain a controller operative to identify and report pump or system anomalies to a technician, to facilitate investigation and correction of any abnormalities before any serious damage to the pumping unit occurs.
A controller for controlling operating parameters associated with fluid flow, speed or pressure for a centrifugal pump for pumping fluid, wherein at least one sensor is coupled to the pump for generating a signal indicative of a sensed operating condition. The controller comprises a storage device for storing data indicative of at least one operating condition and a microprocessor in communication with the sensor and operative to perform an algorithm utilizing the at least one sensor signal and the stored data indicative of the at least one operating condition to generate a control signal, wherein the control signal is indicative of a correction factor to be applied to the pump.
There is also disclosed a method for automatically controlling operating parameters associated with a centrifugal pump according to an algorithm for pumping fluid to a discharge outlet, comprising the steps of storing in memory data values corresponding to predetermined operating conditions, obtaining sensor measurements indicative of current operating conditions, utilizing the sensor measurements and the stored data values to determine calculated data values corresponding to the current pump operating conditions, and comparing the calculated data values with the stored data values and generating a control signal indicative of a correction factor to be applied to the pump when the calculated data values differ from the stored data values by a predetermined amount.